Time Attack

[spannerx]

  260DET said:

With two wheel drive and Nissan multilink rear suspension, what are the suspension's critical areas in regard to rear grip and stability?

My wild guess is reducing anti squat, lighter rear springs than front and ensuring toe in at all times.

And is removing the rear ARB completely ever an option?

Richard Sounds like you know a trick or two with suspension setups are you running rosejoints ? and what were the benefits as i'm just in the suck and see stage.

[Sydneykid]

  Quote

Cheers Gary i;m rebuilding my back end using solid alloy cradle bushes and rose joints in all my arms ect i;m just trying to get a faster reaction out of my suspension.

Gary

There is no doubt that taking out unnecessary movement is a good thing, if done properly. The problems that I see are not in the theory itself but in the physical application of the theory. For example, solid mounting the rear cradle without allowing for adjustment of its angle. Even worse, adjusting control arms with spherical links and not correcting the bump steer. Or using roll centre adjusters without knowing where the actual role centre or the CoG are.

Any the sphincter of the universe can buy a box of bits and bolt them on, but it just makes the handling worse if the knowledge on how to use those bits isn't there. If you don't have the knowledge, experience and the equipment to measure the results its pretty much guaranteed to be a waste of time and money. The underlying problem is the parts themselves are relatively cheap (in time and $'s), but acquiring the knowledge is expensive in that it takes time. Then you require the equipment, scales for calculating the CoG, bump steer guage, wheel alignment equipment etc and the knowledge to use them. Lastly I need the time and $'s to test their effects and optimise the set up accordingly. In a full day of testing, with 1 driver, 4 crew and a suspension engineer/manager I might just optimise the geometry. Provided I have spent a full day before hand doing the homework.

In simple terms, what I have found is if I spend $500 on suspension components I often need to spend 20 times that on optimising them. If I don't do that then it's pretty much guaranteed that I will have wasted the $500. It's the reverse of having a big power engine, you spend $10K on buying the engine and $500 turning it.

Cheers

Gary

[Sydneykid]

  260DET said:

With two wheel drive and Nissan multilink rear suspension, what are the suspension's critical areas in regard to rear grip and stability?

My wild guess is reducing anti squat, lighter rear springs than front and ensuring toe in at all times.

And is removing the rear ARB completely ever an option?

The requirements are no different to any other IRS system;

1. Eliminate the bump steer (not necessarily toe in at all times)

2. Optimise the camber curves to suite the tyres

3. Run the softest possible spring rates that you can within the tyre's working window

4. Adjustable squat

5. Separate adjustment in the shocks for bump and rebound

Number 3 above almost always demands that some rear anti roll be utilised. Let's face it, why would you remove the easiest, cheapest and most effective way to tune the handling balance.

Cheers

Gary

[spannerx]

  Sydneykid said:

There is no doubt that taking out unnecessary movement is a good thing, if done properly. The problems that I see are not in the theory itself but in the physical application of the theory. For example, solid mounting the rear cradle without allowing for adjustment of its angle. Even worse, adjusting control arms with spherical links and not correcting the bump steer. Or using roll centre adjusters without knowing where the actual role centre or the CoG are.

Any the sphincter of the universe can buy a box of bits and bolt them on, but it just makes the handling worse if the knowledge on how to use those bits isn't there. If you don't have the knowledge, experience and the equipment to measure the results its pretty much guaranteed to be a waste of time and money. The underlying problem is the parts themselves are relatively cheap (in time and $'s), but acquiring the knowledge is expensive in that it takes time. Then you require the equipment, scales for calculating the CoG, bump steer guage, wheel alignment equipment etc and the knowledge to use them. Lastly I need the time and $'s to test their effects and optimise the set up accordingly. In a full day of testing, with 1 driver, 4 crew and a suspension engineer/manager I might just optimise the geometry. Provided I have spent a full day before hand doing the homework.

In simple terms, what I have found is if I spend $500 on suspension components I often need to spend 20 times that on optimising them. If I don't do that then it's pretty much guaranteed that I will have wasted the $500. It's the reverse of having a big power engine, you spend $10K on buying the engine and $500 turning it.

Cheers

Gary

Gary understand where your coming from but yes in every change that i make i will use my alignment equipment to check and i will be using my corner scales and yes will be keeping records. As most parts that i fabricate and machine including rose joints need to be tested. Chow.

[260DET]

  Sydneykid said:

..................................................................

3. Run the softest possible spring rates that you can within the tyre's working window

....................................

Number 3 above almost always demands that some rear anti roll be utilised. Let's face it, why would you remove the easiest, cheapest and most effective way to tune the handling balance.

Cheers

Gary

Why? To transfer as much roll on to the front suspension as possible. Yeh I know thats a obvious answer but with some cars with some suspension systems and often where big power is involved that can work best. Tune with the front ARB, spring rates, etc.

But I see your point, better to be able to tune both ends rather than just one.